Blogics! It’s a logic circuit simulator aimed at beginners. It introduces simple concepts in the design of interactive physical computing systems such as sensors, actuators, processing and their relationship to the environment.

Logic Gates Basic operations of digital systems. Each logic gate has a number of inputs and produce an output accordingly. Each input is a binary value (1 or 0) that correspond to truth values (true or false)

Example: AND gate I will go to sleep if it is dark and I am tired Go to sleep Stay awake = ?

Example: AND gate I will go to sleep if it is dark and I am tired Go to sleep Stay awake ‘Go to sleep’ is true only when ‘dark’ and ‘tired’ are also true.

Example: OR gate I will go to sleep if it is dark or I am tired Go to sleep Stay awake = ?

Example: OR gate I will go to sleep if it is dark or I am tired Go to sleep Stay awake ‘Go to sleep’ is true either when ‘dark’ or ‘tired’ are also true.

Logic models behaviour By specifying the system’s behaviour with logic gates we can determine its outputs according to each combination of inputs.

Interactive systems Inputs Outputs ENVIRONMENT HUMAN Interactive System

Interactive systems Inputs Outputs ENVIRONMENT HUMAN Sensors Actuators Processing

Sensors A sensor converts a physical quantity into an electrical signal. There is an enormous variety of sensors available commercially, often for very low prices: – Sound – Chemicals – Electricity – Temperature – Proximity – Position – Humidity – And so on…

Sensors The signal that a sensor emits varies according to its operating characteristics and the measured physical quantity captured from the environment or from human action. Sensors can be digital or analogue.

Sensors in Blogics! Switch Thermometer Humidity Sensor Button Light Sensor Presence Sensor

Sensors in Blogics! Each sensor measures a different physical quantity in the environment. – Light Sensor: Day/Night – Thermometer: Cold/Hot – Humidity: Wet/Dry – Presence: Someone/No one – Button/Switch: Human Action/No human action

Sensors in Blogics! Sensors in Blogics! are binary, i.e. they are either on or off according to the environment variable they measure. We simulate changes in the environment by connecting a different environment block to the sensor High temperature Output: 1 Low temperature Output: 0

Actuators The other end of an interactive system is the actuation side. Actuators convert an electric signal into mechanical motion. To simplify the jargon, we use the term to denote any component that converts an electric signal into any kind of feedback to the user or the environment.

Actuators in Blogics! LED - light Fan - temperature Buzzer - sound Vibration motor - haptic

Processing The data collected by the sensors is processed by the logic circuit.

Processing We combine logic gates to create more complex logic statements. Example: Turn on a fan if it is dark and hot We add the NOT gate, because the light sensor outputs 1 when it is bright

TTT: Tips and Tricks and Troubleshooting Logic gates (except the NOT) have 3 input ports (bottom, top and left) and 1 output port (right). NOT has 1 input port (left ); and 1 output port (right) When a value is not assigned to an input port, this port assumes the neutral value of the operation. For the circuit to work it is necessary to use wires between logic gates and sensors/actuators. All wires in Blogics! are directional. This means that the direction of the arrows on the wires should always match the direction of the input-output data flow. To delete a block, create a Bin Block and connect it to the block you want to remove. To delete a Bin, create another Bin and connect the two. If a circuit doesn't display the correct output, click on a logic gate to refresh the calculations. If an environment block doesn't seem to be working, check if it corresponds to the correct sensor. A known bug is that even though the NOT block lets you connect blocks to the top and bottom ports it doesn't take into account their values.

Summary We can use logic to specify an interactive system’s behaviour. When we design interactive systems, we need to think about: – what inputs it takes – what sensors do we need to obtain this input from the user or the environment – what kind of output we want to give – what actuators we need to use to provide this feedback to the user or the environment – how to process the inputs to generate the desired outputs